Crazy flyers (4)
I believe the answer is:
bats
I believe this is a double definition.
'crazy' is the first definition.
(bats can informally mean crazy)
'flyers' is the second definition.
(things that fly)
(Other definitions for bats that I've seen before include "Hits" , "Crazy - mammals" , "Those striking" , "Cuckoo" , "Take a stab at the night creatures" .)